Here is what I like about Harry's - this data is all on the phone and viewable between sessions.

Red is the 'reference' lap - my best lap. Gray is the 'selected' lap that I'm viewing data on. You can zoom in on certain parts of the data and it shows you what part of the track the data came from.

You really need the external GPS to get good data - 897 'fixes' with external 10hz gps vs 129 'fixes' with iphone 1hz gps (on a single lap - both 2:06 laps).











I 'zoomed in' on turn 1 to turn 2. As you can see, I'm leaving some time on the table in turn 1 especially. This is a good visual tool to see that with.

IMO - the thing 'lacking' is a chart showing total acceleration (g). And there isn't a way to show braking G's on the colored 'Map'. It only shows lateral acceleration.